Overview of Low-Rank Coal (LRC) Drying

Abstract

Low-rank coal (LRC) drying processes are generally categorized by operating temperature, drying environment, and type of feed or product. Within these broad categories, drying processes differ further according to the type of drying equipment and methods of quenching and stabilizing dried products. This paper focuses on the issue of the quality of products produced from a number of LRC drying processes that are commercial or have been demonstrated at a pilot-scale, including low and high temperature evaporative drying and non-evaporative processes, such as hydrothermal drying. Evaporative processes are usually the lowest cost and are preferred when the dried product is used immediately. This avoids the problems of moisture reabsorption, dust generation and spontaneous combustion associated with LRC transportation and long term storage. Hydrothermal drying followed by. low-rank coal-water fuel production is one of the most promising techniques for eliminating stability problems, while producing a value added fuel that will compete in the heavy oil market, not the steam coal market.